I had just finished giving a talk on the Information Revolution when a young man approached me and said: "What I really want is a brain implant so that I can move massive amounts of information rapidly and painlessly in and out of my head." "You mean so that you can download and upload information without going through the slow eyeball, mouth and ear interfaces?" I countered. "Yes. Isn't that a great idea?" he replied, much encouraged by my reaction. "No. It's a lousy idea," I said, "...unless you are talking about sensor or effector chips," and went on to explain.

If you cannot hear because of inner-ear damage, but your auditory nerve is sound, then a cochlear implant may restore your hearing, as it has for thousands of people who underwent the two-hour procedure: A small receiver is placed within the bone behind the ear, with its two dozen electrodes surgically implanted into the cochlea, where they can electrically stimulate the auditory nerve. An external device, worn behind the ear, picks up sounds, converts them to electrical signals, and conveys them through a tiny transmitter to the implant and hence the cochlea. The auditory nerve then carries these stimuli to the brain where they are perceived as sounds. The same principle applies to people with a deficient retina and a healthy optic nerve. But because vision is more complex than hearing, the precursors to retinal implants are only now being tried on a few human beings. Sensory implants like these that help people recover a lost sense are a great idea.